For example, as shown in Japanese Patent Publication JP-A-2002-19663, a scooter-type motorcycle is constructed such that its body frame includes: left and right lower frames made up of pipe extending obliquely downward and rearward from a head pipe; left and right upper frames made up of pipe extending rearward from the head pipe; and a plurality of reinforcing frames for connecting these left and right frames. In this case, in order to secure sufficient frame rigidity, one needs to widen as much as possible intervals between the left and right upper or lower frames in a vehicle-width direction.
However, if the intervals between the left and the right upper or lower frames are widened in a vehicle-width direction in order to enhance the frame rigidity, a problem arises in that the size of the whole vehicle in a vehicle-width direction becomes large, which widens the rider seat width and makes it difficult for a rider to put his or her feet on the ground in a stable manner.
In view of the foregoing, it is an object of the present invention to provide a motorcycle in which the size of the body frame is restricted from increasing in a vehicle-width direction while exhibiting enhanced frame rigidity. It is also an object to provide an improved body frame for a motorcycle.